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Jan. 5, 1943. J. E. MCDONALD FAN Filed NOV. 8, 1939 2 Sheets-Sheet INVENTOR \7Ew-nv E- Malian/e40 JG? ATTORNEY Jan. 5, 1943.

J. E. MCDONALD 2,307,418

FAN

Filed Nov. s, 1939 2 Sheets-Sheet 2 INVENTOR JbHA/ E MCDONQD aM M ATTORNEY Patented Jan. 5, 1943 FAN John E. McDonald, Boston, Mass, assignor to B. F. Sturtevant Company,

Boston, Mass.

Application November 8, 1939, Serial No. 303,413 5 Claims. (Oi. 170-159) This invention relates to fans utilizing the socalled Magnus efi'ect for moving air.

An object of the invention is to move air in a fan with rotors rotating about the axis of the fan and revolving about their axes.

Another object of the invention is to vary the volume of air moved by a fan having rotating and revolving rotors by varying the speed of revolution of the rotors about their axes.

Another object of the invention is to straighten out the spin of spinning air by the use of rotors revolving about their axes in a direction to produce an opposing spin.

It has been recognized that the so-called "Flettner rotors utilizing what is known as the Magnus effect have the characteristics of air foils and they have been proposed for providing the lift surfaces of airplanes and the like.

This invention utilizes rotors revolving about their axes and rotating bodily about the axis of a fan for moving the air through the fan. In one embodiment of the invention, two cylindrical rotors replace the blades of a propeller fan and are rotated about their axes by a variable speed drive from the rotary fan shaft.

All propeller type fans produce a spin in the air leaving the blades. This invention provides rotors arranged with radial axes and rotated about their axes in a direction to produce a spin opposite to that from any, type of propeller, or for that matter, from any source what-so-ever for straightening out the spin of spinning air.

The invention will now be described with reference to the drawings, of which:

Fig. 1 is a sectional View along the lines l| of Fig. 5 and is a plan view, partially in section, looking downwardly upon a propeller'fan embodying this invention;

Fig. 2 is a partial end view of the friction driving ring supported from the bearing of Fig. 1;

Fig. 3 is a partial plan view of a rotor adapted to be rotated about its axis by the air stream, and which may be substituted for the propeller rotors of Fig. 1;

Fig. 4 is a view looking downwardly upon the upper end of the rotor rotating member of Fig. 3;

Fig. 5 is an end view from the left hand or back side of Fig. 1;

Fig. 6 is a diagrammatic view illustrating the action of a revolving rotor upon a moving air stream, and

Fig; 7 is a vector diagram illustrating the action of the rotor of Fig. 6 as an air moving device.

The purpose of a fan is to provide energy to initiate the flow of air and to add to each unit volume of air a net increase in energy sufficient to compensate for pressure losses. An expression for the addition of energy to each unit volume of air may be written.

w=angular speed of the fan blades. p=air density. C'u1=spin component of the of the blades. Cuz=spin component of th air at the discharge sides of the blade r1=radius at the inlet side. r2=radius at the discharge side.

If no initial spinning actionis given the air entering the fan,

Cu1r1=0 and AE=wp(Cu2T2) In the axial fiow type of fan, the flow is substantially axial without radial divergence. Since it is desired to add equal energy to each particle of fluid, the expression Cuzrz must remain constant across the section of air and at each radius. This is equivalent to saying that the product of the spin component of the air and the radius at which the spin is measured, is constant at each radius directly behind the fan. This product multiplied by 21r,(21rCll2T2) is called the circulation of the stream leaving the blades and is equal to the sum of the circulations of the fan blades.

A'rotating cylinder in still air will induce about itself a circulatory air motion. This motion is of such nature that the product of spin or tangential velocity and radius from cylinder axis is substantially constant at any point in the air field. This product multiplied by 21 equals 21rRV where R is the radius from the cylinder axis and V is the tangential or spin velocity. If there is superimposed upon this circulatory system, a uniform velocity field, a flow pattern as illustrated by Fig. 6 will result. The air stream will be diverted around the cylinder with higher velocities on one side, and lowervelocities on the other side of the cylinder. Such variation in velocity results in a reduction in static pressure on one side, and an increase in static pressure on the other side, of the cylinder.

Since the circulation of each rotor can be written Circulation=21rRV where R=radius of the cylinder and V=tangential velocity of the cylinder the total circulation of Z motors will be Total circulation=Z( 21rRV) This is the value of the circulation in the stream air at the inlet sides of air leaving the fan with the rotors replacing the fan blades. Now

2wCuzrz=Z (21rRV) and Since AE represents the total pressure increase through the fan, the action of the rotors in creating the pressure for providing the desired air volume, may be mathematically calculated as shown.

Due to the nature of air, tests have shown that actual performance is not that as mathematically demonstrated in the foregoing, but that actual rotor speeds should be from two to three times higher than the theoretical ones.

The drawings illustrate the application of the invention to a propeller type fan. Referring now to Figs. 1, 2 and 5, the two rotors ID are attached to the inner ball races H, the outer races being held inthe casing l2. The friction disks I3 are attached to the rotors ID for revolving same about their axes. I

The casing i2 is attached to the rotary shaft H which is rotated in the bearings l5 and I6 through the intermediary of the coupling l1 and motor shaft l8 by any suitable motor (not shown).

The casing of the bearing I 5 is slotted as shown by Fig. 2 to slidably receive the friction ring 19 which is in driving contact with the friction disks 13 attached to the rotors Iii. Upon rotation of the shaft i4 and the consequent rotation of the rotors Iii, the contact of the disks l3 with the ring l9 causes the rotors ill to revolve about their axes.

The speed of revolution of the rotors about their axes may be adjusted by sliding the ring ii! towards and away from the rotors. The rotor speed is greatest when the ring i9 is nearest the rotors due to the ratio between the driving and driven areas. The volume of air moved by the rotors varies conformab y with their speed of revolution about their axes.

The reaction of the rotors with the air is shown by the vector d a ram of Fig. 7. The lower arr w A indicates the direction of the movement of the. air onto the rotor. the vectors .8 indicate the tin speed and e direction f movement of the rotor at a selec ed po nt on its surface. the vector C indic t s the axial component of the air velocit a d the vector D ind cates the vel citv c rrmrm ent of the air enterin the rotor. The vector E indicates the axial oemnnnent of the air leavin the o r. th v ct r P indicates the s in c m nent in the. air leaving the r tor. the vector G indicates he absolut c m nent of the air velocitv at the, d schar e side of th ot r. and the vector H indicates th relati e ve ocity and the direction of the air leaving the, r tor.

The air leavin everv form of propeller fan has a ronounced spin h ch it is desi able to overcome. The. rotors 2n. the axes of which are fixed. are revolved about their axes in a direction to produce a. s in o pos te to that of the spinning air to effective y straighten out the s in.

The rotors 20 are rev lvable on the bearin s 2| about the fixed shafts 22. the outer ends of which are threaded and'extend throu h the fan casing 23 to receive the nuts 24 which hold them to the casing. The inner ends of the shafts 22 are attached to the central hub 25. which in turn is supported on the central shaft 26 held by the support 21.

The friction disk 28 is keyed onto the revolvable shaft ll so as to revolve with it and is in contact with the friction disks 29 attached to the rotors 20. Rotation of the shaft l4 and the disk 28 causes rotation of the disks 29 and the rotation of the rotors 20 about their axes. The rotation of the rotors 20 about their axes is opposite in direction to the rotation of the propeller rotors l0 about their axes so that the spin imparted by the propeller fan is corrected. Such a spin correcting mechanism may be used with any form of propeller fan or to straighten out the spin caused by any other device.

Figs. 3 and 4 illustrate a simple construction for rotating the rotors described in the foregoing directly by the air stream. Each rotor 30 has mounted on its tip, the vanes 3| which are rotated by the air stream and which rotate the rotors about their axes. This form of rotor drive may be used as where it is not desired to vary the volume from a constant speed fan by adjusting the speed of revolution of the rotors as in the embodiment of Fig. 1. Other forms of rotor revol ing mechanisms may, of course, be used.

In the annexed claims, the term: revolving said rotors about their axes in the direction of the desired air movement" refers to the direction of rotation of the air accelerating surfaces of the revolving rotors.

While embodiments of the invention have been described for the purpose of illustration, it should be understood that the invention is not limited to the exact apparatus and arrangements of apparatus described, as departures therefrom may be suggested by those skilled in the art without departure from the essence of the invention.

What is claimed is:

1. In combination with a fan having propeller blades, a plurality of rotors having substantially radially arranged shafts and having stationary shaft supporting means, in alignment with said blades on the downstream side thereof, and means for revolving said rotors around the axes of said shaft in a direction to produce a spinopposing that produced by the rotation of said blades.

2. In combination with a fan having propeller blades and having a shaft for rotating said blades,

a plurality of rotors having shafts arranged substantially radially about said shaft, said shafts of said rotors having stationary shaft supporting means, in alignment with said blades on the down stream side thereof, and means operated through rotation of said shaft of said fan, for revolving said rotors around the axes the shafts of said rotors in a direction to produce a spin opposing that produced by the rotation of said blades.

3. In combination with a propeller fan having air moving means and means for rotating same,

a stationary air guiding casing around said air moving means and having a portion extending to the rear thereof, a plurality of rotors having radial shafts, shaft supporting means attached 5 to said portion, and means for revolving said rotors in a direction to produce a spin opposing that produced by said first mentioned means.

4. In combination with a propeller fan having air moving means and means for rotating same, a stationary air guiding casing around said air moving means and having a portion extending to the rear thereof, a plurality of rotors having radial shafts supported within said portion and having shaft supporting means attached to said portion, and means for revolving said rotors in a mentioned means, means for directing said gas stream in contact with said rotors, and means for revolving said rotors around the axes of said shafts in a direction to produce a spin op- 5 posing that in said stream.

JOHN E. MCDONALD. 

